The present invention relates to a method for braking a vehicle by means of a fluidically triggerable vehicle brake system and to a corresponding vehicle brake system, wherein the vehicle brake system comprises a respective fluidically triggerable brake unit that is assigned to a vehicle wheel and is fluidically coupled to a brake force generator via at least one fluid circuit, wherein a pumping mechanism by means of which at least one of the brake units can be fed with brake fluid regardless of whether the brake force generator is activated, is provided in the at least one fluid circuit in order to convey brake fluid, and wherein control valves by means of which the brake force generator can be fluidically coupled to and disconnected from the brake units and the pumping mechanism are provided in the fluid circuit.
A vehicle brake system of this type is known from the prior art. Thus document DE 101 10 658 C1 and corresponding U.S. Pat. No. 6,672,686, which are hereby incorporated by referenced, disclose a hydraulic vehicle brake system in which two separate fluid circuits can be fed with brake fluid via a master brake cylinder. Two brake units are assigned to each fluid circuit, one brake unit of a front wheel and one brake unit of a rear wheel. To trigger the respective brake units control valves are provided. A pumping mechanism is also assigned to the two fluid circuits, via which the brake units can be triggered via the master brake cylinder independently of a pressure generation. It is consequently possible to achieve electronic control systems, such as an electronic stability program (ESP).
In order to be able to a achieve parking brake effect without significant additional technical complexity, in addition to the functionalities, described for the case of service braking in document DE 101 10 658 C1 and U.S. Pat. No. 6,672,686, of a vehicle brake system of this type, it is also known from the prior art to use the fluid pressure built up via the master brake cylinder and acting on the individual brake units to create a parking brake condition. For this purpose the brake fluid fed to the brake units of the vehicle wheels of the front axle for example is conveyed via the pumping mechanism from the brake units of the front axle to the brake units of the rear axle and then mechanically locks the brake units of the rear axle. In conventional vehicle brake systems this takes place in a condition in which a specific brake pressure is still built up via the master brake cylinder, for example in that the brake pedal is firmly depressed by the driver of the vehicle. However, this in turn means that during activation of the parking brake effect there is a direct fluidic connection between the master brake cylinder and the brake units. As a result vibrations and noise which occur during activation of the pumping mechanism to cause the parking brake condition are transmitted directly via the master brake cylinder, the adjoining brake booster and the brake pedal into the interior of the vehicle, and the driver and additional vehicle occupants can regard this as being disruptive. As a result of activation of the pumping mechanism brake fluid is also inevitably removed from the master brake cylinder, so the brake pedal yields under the pedal actuating force exerted by the driver of the vehicle, and this is again felt by the driver and could be regarded as unpleasant or at least unfamiliar.